The previously fast-rising music video service Vevo is experiencing a sudden freefall in Web viewership, according to the online reach tracker comScore.

Per a recent PaidContent report, Vevo's unique viewership numbers dropped 20 percent in May from the same time in 2011, with circulation down from roughly 60.4 million to just 48.3 million unique viewers each year. Viewing times also declined by roughly 26 percent, with average minutes per viewer shrinking to 77.7 minutes from 105.1 minutes in 2012.

The numbers point to the service's potential problem: a growing inability to engage with music fans. Previously one of the Internet’s most rapidly-growing success stories, Vevo insists that its service – a joint venture from Sony Music Entertainment and Universal Music Group that screens premium music videos on-demand – is simply misunderstood. According to PaidContent, a Vevo spokesperson suggests that comScore’s data is incomplete, failing to incorporate a look at a larger business picture which includes audiences increasingly accessing the service from alternate platforms and devices. Per the site’s source, usage of Vevo’s mobile apps is up 46 percent in the same period, while usage of mobile video streams has skyrocketed 434 percent to top more than 450 million views globally in May.

Currently available on multiple gadgets and formats from iOS and Android phones/tablets to Xbox 360, Vevo can now be accessed by users on many high-tech touchpoints. While ComScore’s metrics may not reflect their impact, nor audience numbers for foreign territories like the UK or Canada in which the service also operates, artists and industry insiders hope these Web-related concerns are just a temporary blip. As Vevo already boasts clips from such oft-debated acts as Azealia Banks and Justin Bieber, we shudder to think what it would take to sustain Internet viewers’ attention beyond them.

UPDATE: ComScore's initial story has since been amended to include the following response from Vevo:Vevo additionally notes that a methodology change enacted by comScore in July 2011 renders our May 2011 – May 2012 comparison of minutes spent by user moot. In fact, minutes spent by user per month watching Vevo content have actually risen since the methodology change.

Vevo also attributes some of the discrepancy to Google’s redesign of YouTube, which has moved away from feeds of most popular videos to a channel/subscriber model.